6 
Ray Tracheids in Sequoia sempervirens. 
or wider at the top, whereas a bordered pit, even if cut obliquely, 
would narrow towards the top. Mr. W. P. Thompson has found a 
similar feature in Abies (in press). 
1 have had access to fossil forms of Sequoia loaned by Director 
Brock of the Geological Survey at Ottawa, and also to a type set 
of S. Penhallowii presented to Mr. 'Thompson by Professor Jeffrey. 
No true ray tracheids were found. However, in S. Penhallowii 
Professor Jeffrey (1904) has noted that there are marginal cells 
which differ from the central cells in width, pitting, undulating 
borders, absence of tanniniferous contents, and presence of crystals 
(p. 327). Since the parenchymatous cells which replace the ray 
tracheids in S. sempervirens are quite different from the central 
cells in several of the features above mentioned, it is suggested that 
the marginal cells of S. Penhallowii may also be derivatives of ray 
tracheids. 
The results of the present work have been to demonstrate the 
presence of ray tracheids, both marginal and interspersed, in old stem 
wood of S. sempervirens. This, in certain features of the structure 
of its annual ring, is comparable to root wood, and so of a primitive 
type. Gothan, to whom we owe our knowledge of this feature, 
compares such old stem wood of the pine to rootwood in another 
respect as well, the fewer resin canals which it contains, and so 
further suggests its primitive character. It is of interest that it is 
in this type of stem—which, though old, yet retains primitive 
features—that ray tracheids have been found ; and especially is it 
interesting since some of these ray tracheids are also of a primitive 
type. This feature makes it probable that when root wood is 
examined, or certain more primitive parts of the stem, ray tracheids 
will also be found. Since wounding appears to recall them in some 
forms (in Cuuuinghamia, Jeffrey, 1908, and Abies, Thompson, 1910) 
it would be interesting to know if such is the case here. No more 
material is available at present for further investigation, but it is 
thought desirable to publish these results at once, since the presence 
of ray tracheids in S. sempervirens has so recently been denied, and 
since the occurrence of the two kinds of pitting on the one element 
affords such a clear demonstration that there is a transition between 
ray tracheids and parenchyma. 
It was on the suggestion of Mr. R. B. Thomson that this work 
was undertaken, and my heartiest thanks are due to him for his 
kindness and constant advice. 
University of Toronto, 1911. 
